The Stovebolt Site Forums The Shop Area Engine Shop Saved a 56 Chevy 3100 from the crusher. ( cant get spark to fire it up)

Hi everyone thanks in advance for any help and info. This is a great site and am getting back into another project I just saved from the crusher.

Truck- 1956 Chevrolet 3100 Short bed Step side. 235 Inline 6 engine 3 speed on the column transmission.

Problems- Cant get spark to spark plugs to fire engine up.

I've replaced the Battery (new 12v),. ignition coil, points, condensor, disributor cap, rotor, spark plugs and wires aleready and still no spark.

The coil is getting 12v from ignition to the positive terminal on coil.

Im not to farmiliar with points distributors and how everything works but from what info I found online and some pictures I have a rough idea and just cant get spark to fire this truck up.

Thanks again for any help!

Did you make sure the points were sitting on top of a lobe (highest point) on the distributor shaft? If you set the points on the flat instead of the peak you won't get any spark at the plugs.

Also, you can check to see if points are opening and closing by taking a test light and placing one end on the wire going to the distributor from the coil. (Should be the negative side of the coil.) Then ground the other end of the test light to the engine block. Have someone turn the ignition switch on and crank the engine.

The test light should go on and off (may flicker) as the engine spins.

If the light stays on, the points are too wide and not closing, if the light stays off the points are staying closed and the point gap is too small.

You can also watch to see if the points are "sparking" as the engine is tuned over while the switch is on.

I spun engine till points were on a lobe (highest spot) Set the new points to .019 from what I found online for specs.

I dont have any one here to give me a hand right now but I took cap off and turned engine over by hand and see the points opening and closing visually.

coil is wired up. Positive side has 12v and negative side is ran to distributor and shows less than one volt.

When ignition is on and I attach coil wire to distributor it sparks and drops from 12v to .42v and positive sides drops to 3.88v.

It that suppoed to happen???

Heres a couple pics of the truck also-

http://i283.photobucket.com/albums/kk292/94sc2/2013-03-18171807_zpsf97ba04e.jpg

http://i283.photobucket.com/albums/kk292/94sc2/2013-03-18171817_zpse4d3a9cf.jpg

http://i283.photobucket.com/albums/kk292/94sc2/2013-03-18171825_zps18109e2a.jpg

http://i283.photobucket.com/albums/kk292/94sc2/2013-03-18144350_zps97defb14.jpg

http://i283.photobucket.com/albums/kk292/94sc2/2013-03-18142029_zps46c74805.jpg

Inside Distributor- http://i283.photobucket.com/albums/kk292/94sc2/2013-03-22221202_zpsbc135e4c.jpg

If the points are closed the voltage should drop. If they are open it should stay the same.

There may be a chance the wire from the coil to the distributor is grounded where it passes through the distributor.

hard to tell from the picture of the distributor, but looks like inside the housing where the points attach to the bolt that goes through the housing, it may be grounded to the housing. It should be insulated from the housing.

Take the wire from the negative side of the coil off the bolt at the distributor housing. Turn the switch on and see if you have battery voltage or close to it), at the end of the wire while it is loose from the distributor. Then touch the wire to the bolt that sticks through the housing and see if the voltage drops while the points are open. If the voltage drops while the points are open, then the points or the bolt where it passes through the housing is grounded. The bolt that passes through the housing must be insulated from the housing. The spring from the points connects to this bolt.

The only time the points should be grounded is when they are closed.

You can also see if the bolt or points are grounding to the housing while the points are open by using the ohmmeter to see if there is continuity between the bolt that sticks through the distributor housing and the housing.

Stick one lead on the screw, the other on the distributor housing. If you have continuity, there is your problem. The bolt should be insulated. Make sure points are open during this test.

I have spark now. Thanks! The bolt that holds points to coil wire was grounding to the inside of distributor. Did a quick fix so it wasnt grounding out. gotta see if i can get replacement pieces that should be in there.

Now I have spark and fuel but its just cranking over not really attempting to run. Is the turning over supposed to be really slow?

I have a video I just took of it turning over- http://s283.photobucket.com/user/94sc2/media/video-2013-03-22-23-19-55_zps8b3720fc.mp4.html

NO, if the battery is good, fully charged, the starter is good, and the batter cables are in good shape it should spin over pretty fast.

But sounds like in the video it's turning fast enough to start.

Might try a capful of gas down the carb throat to see if t will fire.

I tried some gas down carb still same thing. Just turning over not attempting to start.

I removed the carb and cleaned it up. The gas pedal was a little sticky. the throttle choke and carb are all functioning properly.

Still not starting.

Certain the spark is getting to the plugs? You might want to pull a spark plug, or just wire, and make sure a nice blue spark is getting to the plug. Ground the plug while wire is hooked up to it. Crank it over and see that there is spark at the plug.

Does it back fire or make any grunting noises while cranking after putting some gas down the carb? Or just crank?

If it still has the stomp starter, make sure the wire from the small terminal on the starter goes to the + side of the coil. It bypasses the ballast resistor in the ignition circuit to give the coil battery voltage.

I finally got it to start but it wont stay running.

Has good spark now. I cleaned all the fuel lines, carb, gas tank. Has good fresh fuel. Fuel pump is working. fuel seems to be sucking up into carb.

It just wont stay running on its own. Is there a trick with these older carbs? fuel delivery?

Sometimes it's hard to get the small passageways clean even when the rest of the carb looks clean.

Did you soak in some carb leaner overnight, or just spray it clean?

I have had to clean passageways with a small diameter wire. Sometimes you can't clean it enough.

Hard to tell from here. Can you tell if it is going lean on fuel (not enough fuel), or if it is getting rich (too much fuel)?

Did you "kit" the carb with new needle and seat? If so, did you check the float level? Too low and it may not let enough fuel into the carb.

It seems like it will run for a couple seconds if I pump gas pedal a dozen or so times before I try to start it.

Im not to farmiliar with this style carb. I just unbolted carb from manifold and just spray cleaned it. I did not take it apart or rebuild it or anything.

If I manually push throttle from under hood I can see a shot of fuel going into the carb from under where the choke butterfly is.

Im going to look into a rebuild kit for the carb online and see if I can find one.

Your local NAPA or other parts store can get the kit if you take them the tag number.

I bet the inside passage ways are clogged up to the point fuel can't get through them. But it's a good sign the accelerator pump works.

Good luck. Sounds like you're getting there one step at a time.

Did you check the operation of the carb choke. I assume it's a manual choke. On my 1950 3100 w/216 it has a manual throttle cable in addition to the manual choke cable. I had this problem originally, but if I set the choke properly to get it started I then set the manual throttle cable so the engine has enough rpm to keep it running until warmed up. If it won't stay running after it's warmed up, then I would think it's a carb problem. On my 50 I have a single barrell carb, which was very easy to overall and the kit wasn't to expensive. When you have the truck running, hook up a vacuum gauge to one of the ports on the carb to see if you have good vacuum. Don't recall what the vaccum is for your 235. If there's any vacuum leaks then that could contribute to the other carb problems. As mentioned in an above post, be sure to set the carb float properly to insure proper fuel flow. One last thing, although you have spark now, is it a good strong spark? On my 50 I have a braided copper ground strap between the engine and the frame. Initially this was aproblem for me getting spark.

Ill check tomorrow to see if I can get the carb kit and have some fun cleaning and rebuilding it.

Im not sure if it had a choke and throttle cable. I'll have to check into that. It only has manual choke cable hooked up. I dont see any other cables or hook ups for another cable.

Thanks for the replies!

You might want to bypass the trucks gas tank, connect a hose to the inlet of the fuel pump and the other into a gas can.

I cleaned the gas tank and all lines. Everything was clean with no rust. I have an inline clear fuel filter right before carb and it is getting clean fuel to it.

Since you didn't tear the carb apart, that's likely where the problem lies. You can kit it, or perhaps get one ready to put on.

Best if you can to soak your carb in a bucket of carb cleaner overnight, then you will have better luck getting the passages clean.

I tore it apart last night. Was working late

I let it sit in cleaner. I tried to call NAPA this morning to order the rebuild kit but there closed on sunday here by me. who knew .

Guess ill have to wait till tomorrow to order it. I also downloaded and printed out the carb repain manual. ( Great disassembly and assemble instructions) Great help at figuring carb out.

Hopefully I will get it all cleaned and operational this week.

Website with Rochester Carb Manual- http://www.newagemetal.com/pages/ServiceProcedures/B/1964/index.htm

Some pictures of carb teardown. Looked pretty bad inside.

http://i283.photobucket.com/albums/kk292/94sc2/2013-03-24001302_zpsb7883688.jpg

http://i283.photobucket.com/albums/kk292/94sc2/2013-03-24001341_zpscb930f09.jpg

http://i283.photobucket.com/albums/kk292/94sc2/2013-03-24002004_zps1446f96d.jpg

http://i283.photobucket.com/albums/kk292/94sc2/2013-03-24002011_zpsdd0cdea8.jpg

http://i283.photobucket.com/albums/kk292/94sc2/2013-03-24002018_zpsfe1ef872.jpg

A little dirty, but not as bad as many I've seen. Should clean up and work.

Just got a call from auto parts store and said they got rebuild kit in.
Going to pick it up and then put ill all back together.
Hopfully the rain will stop today to.

Send the rain to Texas. We are needing some pretty badly here in North Central Texas.

I wish I could. Its just cold and wet here in new jersey.

I got the carb back together and put back on truck. It ran for a couple minutes then cut off like its not getting fuel.

I cleaned everything very throughly and put it back together while watching a good video on youtube with alot of good info.

I'm going to go back outside and see what happens.

Do you have it connected to the trucks gas tank?

I hooked everything up. getting fuel to fuel pump and its puming to carb.

Judging by the photo it appears that the points are closed when they should be open.

(Based on your photo of the distributor)

Move the engine around till the tab on the points is on one of the high spots on the distributor cam. Loosen the screw closest the side of the distributor. The screw next to the contacts is what you use to adjust the point gap with. While turning the adjustment screw use a .016 feller gauge (or a match book cover) to set the gap with. You want a snug fit.

There is a possibility that the points are corroded and need to cleaned. You can use a file card like the girls use to file their nails with. There is also possibility the the condenser -- the round item inside the distributor -- is no good. I would replace both to eliminate this as a possibly source of the problem.

If you have an ohm meter check the points while their open for continuity. If you have continuity while the points are open then the points are shorted out and you will get no spark.

The rotor -- the item sitting on the top of the distributor shaft -- might have a tiny crack in it. A tiny crack in the rotor will act like a wire and redirect the spark to the distributor shaft rather than the distributor cap. A crack in the distributor cap could do the same thing redirecting the spark the distributor's edge. A cracked distributor cap can also cause a consistent miss when the engine is running.

I hope this helps I'll check back and see if you have spark yet


Walt Williams
La Verkin, UT

I have good spark...

It's sems like its not getting enough fuel. My dad and I were out all day trying to figure it out. we cleaned the gas tank and all the lines again. we even hooked up a electric fuel pump and still the same thing. ( It just cuts out and stalls)

Here is a video. 2:50 in it just cuts out and its been worse after I took the video. -

http://s283.photobucket.com/user/94sc2/media/video-2013-03-26-18-14-39_zps02d99595.mp4.html


I guess the only thing I can do is tear the carb back down and go over everything again.

When it shuts down or stops, if you put a little fuel down the carb throat will it start right back up until it burns that out?

Does the accelerator pump still push a little fuel into the throat when you work the throttle shaft?

If it starts right back up you might can eliminate electrical problems. If it won't, might double check the spark at the plug when you you have a no start situation.

It would start after a few stomps on the starter switch.

I pulled the carb back apart and took a look at everything again and recleaned everything and reinstalled it after it was put back together.

Then it wasn't starting at all. Just turning over. I got a little angry and just held the starter pedel down and it stayed running while starter was engaged. So I put a spark tester on a wire and plug and sure enough only had spark when I held pedal all the way engaged or played with it.
Could it be bad starter? Pedel? Something with the wiring?

I just down know. And don't want to dump money into parts that aren't bad.

Thanks everyone for all your help so far.

Put one end of a test lead on the battery positive terminal and the other end on the + terminal of the coil. See if it starts.

Don has a great idea. That test will bypass the ignition switch and ballast resistor and should let the truck continue to run if the problem is due to electrical issues. And it sounds like it is.

Maybe the old ignition switch is breaking down. Does it have a ballast resistor between the ignition switch and the coil?

You said you put a new coil on. Does it happen to have a built in resistor? It shouldn't have a built in resistor if you have a ballast resistor in the line from the ignition switch to the + side of the coil.

I went out and tried to start it normally. It started and ran for like 3 minutes then lost spark. I jumped the wire from + side of battery to + coil and it started right back up.

I'm not 100% on the ballast resistor. But I believe there is one on the firewall. (white/ plastic) it has 12v to top and bottom wires going into it.

But no 12v to coil until jumped. I don't believe coil has a resistor in it.

I don't know that a ballast resistor can work for a bit, then quit. Then after cooling off work again. But I guess anything is possible.

The ballast resistor has a wire that goes from it to the positive side of the coil. The other wire from the ballast resistor goes to the ignition switch. There may also be another wire from the small terminal on the starter that either hooks up at the + side of the coil, or at the ballast resistor on the same terminal as the wire from the ballast resistor to the + side of the coil. (Don't remember the color off hand.

When the truck quits, take a volt meter or test light and see if you have power at the + side of the coil. You should, won't be 12 volts because it's going through the ballast resistor. If no power, go to the ballast resistor and see if you have power on either terminal. If you have power on the side that feeds the +side of the coil, then the wire between the coil and the resistor may be broken inside the insulation.

If you don't have power to either terminal on the ballast resistor then the problem is in the supply from the ignition switch, or even further back. I think the ignition switch is supplied power directly off of the amp meter.

Ballast resistor is on the firewall on that truck, white in color and is ceramic. Maybe 2 1/2 or so inches long, about 1/2 inch wide and thick.

I went out, it started up fine with 12v to coil and ballast resistor.

A minute later stalled and had .24v to ballast in and .12v to ballast out to coil wire.

That won't quite run it. Sounds like you're losing your 12 volt supply from the ignition switch.

Could be corroded wires at the switch, could be the switch, could be the connections on the back of the amp gauge.

There is a large wire that comes off the main battery cable terminal on the starter that goes inside the cab and feeds the amp gauge, then everything else starts feeding off the amp gauge. Maybe that main wire is bad.

Thanks, I'll check out that wire and ignition switch wires.

I've been working on the truck on and off for the past couple days. I fixed a couple questionable wires that were frayed and chewed up looking. I'm pretty sure the main problem lies inside the ignition switch.

I'm going to replace the ignition and ballast resistor. I'm pretty sure that will fix the problem.

Thanks again Roy and everyone else who chimed in on helping me out trying to figure this truck out.

Main thing is done! (got it running and driving) now just have to figure out how to get it to stop.